Method and apparatus for separating oil and water and measuring the amount of oil

ABSTRACT

A method of measuring relatively small amounts of hydrocarbon oil contained in water, or other immiscible liquids including mixing a solvent and a conductivity additive with the oil and water or immiscible liquid, hereinafter termed &#34;water&#34; as it will be the most prevalent use, to form a mixture. The solvent is water rejecting and extracts the oil from the water. A method of producing a chemo-conductivity additive to render the electrically non-conductive oil of the mixture electrically conductive without rendering the solvent conductive or adding to any existing water conductivity. The amount of oil is electronically ascertained by measuring the conductivity of an electrical current passed through the mixture after the oil has been rendered conductive. A novel apparatus is provided to perform the process. The apparatus comprises all the elements for carrying out the process including a separating funnel, measuring beaker, electrode assembly, electronics assembly and both analog and digital displays. In particular, the unique electrode assembly is specially designed to enable conductivity measurement of the electrically conductive-rendered oil.

BACKGROUND OF THE INVENTION

Both unsaturated and saturated hydrocarbon oil in the parts per millionor parts per billion range, is often present in water or in otherliquids which are immiscible with oil. In many cases, variouscontaminants, such as salt, algae, silt, phenols, emulsifying agents,radioactive materials and other contaminants may be present. It is oftennecessary or desirable to measure the quantity of oil present in such amixture. For example, it may be necessary to determine the amount of oilpresent in water being discharged to make certain that there isinsufficient oil to have any deleterious effect on the environment.Also, it is sometimes desirable to monitor a liquid stream to determineif the quantity of oil present in the stream is sufficient toeconomically justify recovery of the oil. In addition, radioactive oilmeasurement can be of significant value.

The oil with which the present invention is primarily concerned isdescribed herein as all saturated hydrocarbon oils, and thoseunsaturated oils which will not react in water by intermingling ofatoms. For example, the oil may be crude oil or single or multiplesaturated fractions thereof ranging, for example, from asphalt to cleanlower-specific gravity crude to the very difficult to measure or treat"acid sludge" and/or BS&W present in the bottom of tanks as found inpetroleum production. Also, the oil may be of the type obtained frompetroleum refining and contain a wide series of hydrocarbons fromdistillation, including, for example, the paraffin series (methaneseries C_(n) H_(2n+n)), napthene or cycloparaffin series olefins (C_(n)H_(2n) -2 less H atoms), ethylene and aromatic series, and where therefinery has attendant chemical plants, oils from distillate basedinsecticides, etcetera.

Quantitative tests for oil in water or other liquids immiscible with oilare possible. For example, testing procedures using photometrics (incertain cases only) eight-hour hexane extraction in all cases, dyes (incertain cases only), infrared scan, spectrophotometry in all cases,conductivity (until this disclosure-useable in solvent-oil only), andothers are known, but will not function in all cases, such ascentrifuging, fluorescence, etcetera, as listed by the U.S. Departmentof Commerce S-85:950/SER:4324. However, these methods are carried out ina laboratory or in oxygen tests partially "fixed" in the field to holdsample enroute to laboratory, and this requires that samples be taken byskilled technicians, (if results are to be accurate, a service noted inall certified public testing laboratories' list of their function andcosts), from a field location, which is often remote, to the laboratory,for testing. The time required for transporting the test sample and thetest itself may result in substantial delay of the order of days betweenthe time the sample is taken and the time the test results are obtained.Although some of the quantitative-oil-only testing equipment ispurportedly portable, this equipment requires electrical power lines andso is not portable in the sense that it can be easily manuallytransported from location to location without requiring any externalhook-ups of any kind, or the equipment may require a support system ofsuch high weight or bulk as to be impractical to transport.

There are several portable oil monitors which use conductivity tomeasure the static charges on flammable liquids of a single composition.Information on these in the United States, United Kingdom, Germany,France and other countries has been studied and the manufacturers havereported that their devices will not operate where the sample to betested for oil includes a mixture of water and oil and may contain morethan one specific hydrocarbon fluid, particularly when the samplecontains suspended debris.

SUMMARY OF THE INVENTION

This invention provides a new method and apparatus for determining theamount of saturated hydrocarbon oil and all unsaturated hydrocarbon oilsthat will not support a reaction in the presence of water or in a liquidimmiscible with the oil. The apparatus is entirely portable and can beeasily manually transported from location to location. As one of itsnovel features it is a light weight, and small support system having anelectronic circuit which weighs 17 grams. The support system, case,supply of solvent, and power cells, in combination weigh less than 17pounds (7711 grams). It may also be permanently installed if desired.When used as a portable unit, no external hook-ups, such as powerconnections, are required. Although the method of this invention can becarried out in a laboratory if desired, it is particularly adapted forthe field at or near the location where the sample is taken. Althoughthe described embodiment of the invention is sophisticated, it is also arugged and simple instrument because of the use of micro-monolithicintegrated substrates which obviate the use of all conversion charts,correction factors and mathematics permitting the tester toquantitatively obtain oil, and also perform the conversion functions.Thus the apparatus can provide a direct read-out and no special skill isrequired to operate the apparatus, to perform the method or to interpretthe results.

Briefly stated, one aspect of the invention involves the separation ofsmall amounts of hydrocarbon oil from an immiscible liquid, such aswater. To obtain separation, a sample of the hydrocarbon oil entrainedin the immiscible liquid is mixed with a solvent which is not soluble inthe immiscible liquid and which extracts the oil from the immiscibleliquid. The solvent not only extracts the oil, but rejects theimmiscible liquid to form a solvent-oil mixture. The solvent-oil mixturehas a higher specific gravity than the immiscible liquid so that theimmiscible liquid and its dissolved and suspended solids float on thesolvent-oil mixture within a mixing container. Materials that are inertor that will not remain in the immiscible liquid phase, form in a layerat the interface of the differing specific gravity liquids. Thesolvent-oil mixture can then be poured, drained, or otherwise removed,or partially removed, from the container. By removing less than all ofthe solvent-oil mixture, any contaminants present in the sample are leftin the container.

Separation of the oil from the immiscible liquid and contaminants may bean end in itself, in that the aforementioned process provides clean oilin minutes by the "liquid filter" concept portion of this inventionnecessitated by a portable rapid result instrument whereas conventionalfiltration wherein a liquid is passed through a minutely porous solidmedia, a material such as agglutinous algae, would plug the porous"solid" media immediately. Another feature of the invention is toascertain the quantity of oil present in the sample. To accomplish this,a conductivity imparting additive is mixed with the oil and the solvent.The conductivity additive is added in an amount that imparts a desireddegree of polarity to bring the electronic circuit up to sufficientcurrent passage to be stable and render the oil conductive. However, thesolvent which is preferably essentially non-conductive, is not renderedconductive by the conductivity additive and the immiscible liquid is notrendered additionally conductive by the conductivity additive. It mayappear that additional conductivity imparting to, for example, a waterphase is not important as this phase is discarded after its oil has beenextracted. However, this would remove some polarity imparting additivewhich would vary with each differing water phase or sample and thus aconstant amount of polarity imparter would not be available for the oilphase and cause innaccurate results. Water distilled 18 times in quartzglass has a dielectric constant of 80.37 at 20 degrees centigradewhereas petroleum oil has a dielectric constant ±2.0 at 20 degreescentigrade or 0.025 as much. An electric current is then passed throughthe conductive oil mixture to obtain an indication of the amount of oilin the mixture.

It has been found advantageous to utilize a pair of concentricring-shaped electrodes to pass the electric current through theconductive oil mixture as largest area in smallest space is obtained.These electrodes are of equal area obtained by placing equidistantcircular holes of a total area equal to the difference between the areasof the outer circle and the inner circle thus making each electrode ofequal size as well as providing better liquid flow through the electrodegap. The electrodes can be spaced very closely, for example, at a onemillimeter gap, thus perfect concentricity is not required as at evercloser proximity it has been ascertained that the average spacingbetween the electrodes becomes determining by the law of diminishingreturns. This averaging effect is not limited to concentric circularelectrodes but applies to flat plates and other configurations as well.

Such a feature is of particular value in a portable, typically roughlyhandled apparatus, and is particularly advantageous in a system designedto indicate parts per million or parts per billion oil. The conventionalone centimeter spacing used to provide volumetric units in cubiccentimeters, would be disadvantageous because a lack of concentricity ofthe spaced plates of the electrodes would be determining. In thisinstance however, the smaller gap might at first glance present aproblem because of the use of a conductive additive of finite butcolloidally dispersed metal or metal compound which is attached to thepetroleum oil and produces a fluid with poor circulation due to greaterfriction between close surfaces, as well as a tendency of the charges toorient themselves North and South with respect to the current flow. Theresult would be meter drift towards less conductivity. However, theinstrument is designed to include three Alnico IV permanent magnetsoriented equidistantly outside the glass vessel (25 ml beaker) containerand their resultant magnetic field pushes the electrons to yield a fluidmixture having sufficient circulation to prevent such meter value drift.

This is a novel concept in electrodes. However, it is a proven conceptin research in other arts. By way of example, a cyclotron operates on asimilar principle in which continued magnetic force "kicks" causesneutrons to move ever faster until almost reaching the speed of light.

Prior art, disclosed in earlier patents (by way of example, see U.S.Pat. No. 2,518,758), relates to inventions currently used in laboratorywork, involves a far less efficient method, inappropriate for field use,and consists of the use of a slave magnet inert bar placed on the bottomof the vessel. Outside the vessel bottom a motor driver rotating anothermagnet, drives the slave magnet in the liquid thus providing mechanicalstirring.

The above disclosed, entirely self-supporting magnetic motion imparter,is a unique concept developed for the particular needs of a portable oiltester. However, the above disclosed unique magnetic motion impartingconcept is not to be limited to use in the presently disclosedinvention, but may, as those familiar with the art will now understand,be used in other systems not necessarily relating to the presentinvention.

By extracting the oil from 200 milliliters of sample into 20 millilitersof solvent, a concentration oil factor of X10 was obtained. However, nowit will be understood that the unique electrode of the present inventionalso provides a gain in oil concentration of additional factor byspacing the electrode plates one millimeter apart as opposed to thestandard 1 centimeter. Experimentation by the applicant has shown thatthe decrease in plate spacing produces a non-linear result and an actualgain factor of 22.5 times in concentration of oil presented to theelectronic measuring circuit of the present invention.

The instrument includes an electrical circuit which enables a directread-out of the quantity of oil present in the sample on various scales,including parts per million and parts per billion.

The invention, together with further features and advantages thereof,may best be understood by reference to the following description takenin conjunction with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three dimensional view of an embodiment of an apparatus usedfor carrying out the process of the present invention;

FIGS. 2 and 3 are more detailed top and front views, respectively, ofthe apparatus illustrated in FIG. 1;

FIGS. 4 and 5 are plan and elevation views, respectively, of a portionof the apparatus of the present invention illustrating the manner inwhich certain steps of the inventive process are carried out; and

FIG. 6, comprising FIGS. 6a and 6b, is a detailed schematic diagram ofthe electronics portion of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The first step in the process of this invention is the extraction of oilfrom water or other immiscible liquid and suspended solids. Hydrocarbonoil tends to float on water, and so extraction of the oil where largeamounts of it are present, such as a contiguous layer, can be done inmany obvious ways. However, when oil is present in parts per millionrange, such as one to one thousand parts per million or in the parts perbillion range, such as occurs in radioactive oils, the presence of theoil may not be discernable or quantitatively judged by the naked eye. Inthis situation, the extraction of the oil from the water is a much moredifficult problem.

The oil can be advantageously extracted utilizing a solvent which isessentially not soluble in the immiscible liquid, and the extraction ofoil from water using tetrachloromethane, (CCl₄) hexane, petroleum ether,etcetera. The solvent extracts the hydrocarbon oil and rejects theimmiscible liquid, and also rejects solid or dissolved solids in waterand the contaminants or debris. By mixing the solvent with a samplecontaining saturated hydrocarbon oil (or unsaturated hydrocarbons thatwill not enter into any type of relation with water) and the immiscibleliquid, the solvent extracts the oil from the liquid to form asolvent-oil mixture. The degree to which the solvent rejects water canbe varied to a very small degree, however, the solvent preferably has awater rejection constant in the range of 0.08²⁰, water content.

To bring about separation of the solvent-oil mixture from the immiscibleliquid, the mixture and the liquid preferably have different specificgravities. Thus, following mixing, the heavier component settles to thebottom of the mixing container, and the lighter components rises. Thus,the resulting solution is layered, with the solvent-oil mixture being inone layer and the immiscible liquid being in a second layer.

Preferably, the solvent-oil mixture has a higher specific gravity thanthe specific gravity of the immiscible liquid to assure that theimmiscible liquid will float on the solvent-oil mixture. One importantadvantage of this is that many of the contaminants, such as silt, algae,etc., tend to float on the top of the relatively high specific gravitysolvent-oil mixture. More specifically, the contaminantscharacteristically float at the interface between the solvent-oilmixture and the immiscible liquid. Thus, not only is oil separated fromthe immiscible liquid, but also from the contaminants contained in thesample.

Because the solvent-oil mixture is primarily made up of solvent, thespecific gravity of the mixture is essentially the same as the specificgravity of the solvent. In order that the immiscible liquid and thecontaminants will float on the solvent-oil mixture, the specific gravityof the solvent must be selected in relation to the specific gravity ofthe immiscible liquid. For example, when the immiscible liquid is water,the specific gravity of the solvent is preferably in the range of 1.3 to2.5 or greater with a specific gravity of approximately 1.6 beingpreferred.

The amount of solvent used for test is calculated on the highest testorconcentration of oil range of the test instrument. Much higher rangescan be set, but usually that is unnecessary. The volume of solvent mixedwith the sample is also preferably sufficient to provide a layer of thesolvent-oil mixture of workable thickness in the container. Thisfacilitates physical separation of the solvent-oil mixture from theimmiscible liquid by draining the former from the bottom of thecontainer. By draining less than the full amount of the solvent-oilmixture from the container the P.P.M.'s are not changed, thecontaminants are left in the container physically separated from thesolvent-oil mixture drained from the container. For field testing a 75%withdrawal is preferred as this leaves 25% in the cone shaped vessel sothat the operator does not have to make an exact removal. Thisseparation of the oil from the immiscible liquid may be an end in itselfor additional operations may be performed on either or both of theseparated components.

In addition to the characteristics noted above, the solvent is alsopreferably inflammable or at least of low-vapor pressure. When theextraction of oil is for the purposes of measuring the amount of oil inthe sample, then the solvent should be essentially non-conductive. Forexample, the solvent may have an electrical conductivity of the order of4×10¹⁸ or a dialectric constant of approximately 2.2 or less. Varioussolvents usually of the chloro hydrocarbons, including the solvents setforth in the table below meet these requirements:

    __________________________________________________________________________                           Conductivity                                                       Sp. Gr.                                                                            H.sub.2 O Reject                                                                    as Dielectric                                          Solvent     at 20° C.                                                                   Constant                                                                            Constants                                                                            Flam.                                                                             Viscosity                                   __________________________________________________________________________    tetrachloro-                                                                              1.595                                                                              0.08.sup.20                                                                         2.238  0   0.96                                        methane/                                                                      CCl.sub.4                                                                     tetrachloro-                                                                              1.631                                                                              0.00  3.400  0   0.90                                        ethylene/                                                                     C.sub.2 Cl.sub.4                                                              tetrachloro-                                                                              1.602                                                                              0.003 7.800  0   1.60                                        ethane/CHCl.sub.2 --CHCl.sub.2                                                __________________________________________________________________________

Although the solvent and the immiscible liquid can be mixed in differentways, preferably they are mixed in a transparent mixing container havinga drain valve at the bottom and a fill opening at the top which can besuitably closed as by a stopper. The mixing container preferably hasgraduations so that a representative sample of any one of a number ofknown volumes can be poured into or otherwise provided in, the mixingcontainer. The solvent is poured from a container, such as a beaker,through the fill opening into the mixing container. The fill opening isclosed with the stopper, and the solvent and sample are manually andviolently shaken up and down for a time, such as 30 seconds, which isnormally sufficient to completely mix the solvent and the sample. Atleast once during this mixing period, the agitation is terminated andthe stopper momentarily removed to vent any gas pressure within themixing container.

After termination of the agitation, the mixing container is manuallymoved in a circular manner to give the sample and solvent a swirlingmotion until the heavier solvent-oil mixture settles to the bottom ofthe mixing container and the lighter immiscible liquid floats on top ofthe mixture. When the immiscible liquid is water, it is ordinarilyclear, although depending upon the particular sample, it may be somewhatcloudy. The solvent-oil mixture, on the other hand, has a brownishcolor. If the upper phase of the mixing container does not become clearof brown color, the agitation should be continued until the upper layerbecomes relatively clear. If the upper layer does not become clear withcontinued agitation, then insufficient solvent has been added to extractall of the oil from the sample. For example, if the amount of solventadded was sufficient to extract 1000 ppm of oil and the upper phaseremains brownish after continued agitation, the sample contains over1000 ppm of oil. This can be used, if desired, as a quick go-no go testfor the amount of oil contained in the sample.

The solvent-oil mixture can be utilized in accordance with the teachingsof this invention to determine quantitatively the amount of oil in thesample. To accomplish this, a conductivity additive is mixed with theoil and the solvent. Preferably, the conductivity additive and thesolvent are pre-mixed and are mixed together with the sample using theprocedure described above to substantially simultaneously achieveextraction of the oil from the sample and the rendering of the oilconductive. However, if desired, the conductivity additive may be addedafter addition of the solvent.

An important characteristic of the conductivity additive is that it mustmake the oil conductive while leaving the other components, e.g., theimmiscible liquid, the debris and the solvent, non-conductive.

When the conductivity additive, the oil and the solvent are mixed, theoil is rendered electrically conductive, and the solvent remainsessentially non-conductive. As the oil is the is the only electricallyconductive component of the resulting mixture, the amount of oil in thesample can be measured by passing an electric current through themixture. Accordingly, the greater the quantity of oil, the more currentthat can be carried through the mixture for a given voltage.

It is important that the conductivity additive not render the solventelectrically conductive. If both the solvent and the oil wereconductive, it would not be possible to accurately determine the amountof oil present from the conductivity of the resultant mixture becausethe oil would characteristically form only a small percentage of thetotal mixture.

The conductivity of the oil increases with increased volumes ofconductivity additive up to a threshold. Beyond the threshold, additionof more conductivity additive will not increase the conductivity of theoil. However, it will not have any deleterious effect. Accordingly, thepreferred amount of conductivity additive is the amount which raises theoil to its maximum conductivity level.

Various kinds of conductivity additives which meet these requirementscan be used. For example, colloidal metal-containing particles can beused to render the oil conductive without rendering the solventconductive. The colloidal metal particles can advantageously bedispersed in the solvent which is used to extract the oil and should beof a size small enough to remain permanently dispersed in the solvent.For example, particles having one dimension no greater than 0.2 micronswill remain in suspension in the solvent for long periods. It isbelieved that the colloidal metal-containing particles are adsorbed onthe hydrocarbon oil without penetrating the oil molecule. This impartsconductivity to the oil without rendering the solvent conductive.

Various conductive metal-containing particles which are not soluble inthe solvent and the water phase can be utilized, such as chromiumdicarbide (Cr₃ C₂), chromium silicide (Cr₃ Si₂) and silver peroxide (Ag₂O₂).

A colloid is a finite solid particle insoluble in its dispersal mediumwhich will not combine or be absorbed with the dispersal medium andshould not be capable of being filtered out. The stable hydrophobiccolloidal particles of suitable metal compounds with their inherentexcess atoms appear to be in true solution as a refractive plane or evenTyndal effect does not reveal them. When the solvent and itssolvent-rejecting colloid additive are mixed with saturated hydrocarbonoils at the same time, it is believed that the excess negative chargedcolloid is adsorbed on the static oil and unbalances its charges. Theunbalanced charges seek balance, and the non-polar charges are forced tomove. When movement of charges occurs, the oil is no longer highlynon-polar, but rather has a degree of polarity of conductance for chargemovement sufficient to measure electronically.

Many metals can be rendered colloidal. However, to be used with oil andbe adsorptive, solvents and metal-containing particles must be insolublein water in the oil extraction solvent. Furthermore, the colloidalmetal-containing particles should have a dielectric constant higher thanpetroleum oil at 2×10¹⁶ r/CM³ where r is resistivity in Ohms and haveexcess negative charges. Alkaline earth metal oxides that formhydrophilic hydro oxides which are water bonded, should not be used. Itis preferred to disperse a single alkaline earth metal rather than amixture of metals, and it should be combined as an insolubleirreversible compound from which a gel is made by mechanically reducingto less than 0.2 microns. This enables dispersion of the colloidal metalcontaining particles without chemical assistance.

An alternative to the use of colloidal metal containing particles is theconductivity additive described in U.S. Pat. No. 3,126,260. This patentdiscloses a conductivity additive in the form of an organic compositionwhich consists essentially of a salt of a polyvalent metal and analkylated salicyclic acid containing at least one alkyl substituenthaving eight or more carbon atoms and a polymeric material which issoluble in the organic liquid and which contains at least one acidgroup. The polyvalent material may be, for example, chromium, and thepolymeric material is not essential. One such conductivity additive isavailable from Shell Chemical Company as ASA-3 Anti-Static Additive.

Having extracted the oil from the sample and rendered the oilconductive, the quantity of oil in the sample can be determined bypassing an electric current through the mixture utilizing the apparatusshown in FIGS. 6a and 6b. One advantage of this invention is that itprovides a method and apparatus for measuring accurately extremely smallvolumes of oil in the sample. It is important to note at this juncturethat one factor contributing to this advantage is that the oil is, ineffect, concentrated as a result of the extraction of the oil from thesample. For example, if the original sample contains 200 milliliters and20 milliliters of solvent are added to the sample, then all of the oiloriginally contained in a 200 milliliter volume is now concentrated in a20 milliliter volume of solvent. Thus, in this particular example, theoil extraction step concentrates the oil on a volume basis by a factorof ten, and this facilitates the taking of conductivity measurements.

Now that the steps comprising the inventive process of the presentinvention have been delineated in detail, a novel apparatus forperforming that process will now be described in conjunction with FIGS.1 through 6.

As indicated in FIG. 1, the portable oil monitoring apparatus 10 of thepresent invention is an entirely self-contained unit comprising all theapparatus to carry out the steps of the process described above.

As FIG. 1 illustrates, monitoring apparatus 10 includes a cover 12 whichis fitted to enclose the top of the apparatus to protect the interiorcomponents at times when the apparatus is either being stored or carriedto and from the field site. Further shown in FIG. 1 is a separatingfunnel 14 that is conveniently mounted by appropriate brackets againstthe inside top wall of cover 12. In addition, a solvent container 16 anda measuring beaker 18 are also included so that all the devices fortaking a sample, mixing the sample and producing the appropriate ratioof solvent and sample are readily available to the user along with theapparatus for measuring the parts per million or parts per billion ofoil in the sample as will be hereinafter described.

The remaining elements of the apparatus, as viewed in FIG. 1, come intoplay in the novel process of the present invention in actually measuringthe conductance of the prepared test sample. These elements include anelectrode assembly 20, an instrument front panel 22 upon which aremounted a current meter 24 and a fuse holder 26, digital display 28,electronic circuits mounted on a printed circuit board within assembly30, appropriate power cells 32 to power the unit in the field away fromany form of electrical power source and potentiometer 34 which is usedto provide appropriate adjustments to the circuit to achieve an accuratereading of the oil content on current meter 24 and digital display 28.Meter face roll bars 38 protect the meter from adjacent objects againstwhich apparatus 10 may be stored.

FIGS. 2 and 3 provide more detailed views of the fully assembledinstrument of the present invention with cover 12 in place and the unitin condition for being carried to the site for the oil measurement. InFIG. 2 cover 12 is shown partially broken away to reveal separatingfunnel 14 in its stored position, electrode assembly 20, electronicsassembly 30, digital display 28 and potentiometer control 34. Inaddition, one may observe partially exposed measuring beaker 18. On theleft side of FIG. 2 and shown in dotted lines, is solvent container 16.In addition FIG. 2 provides a top edge view of the current meter 24.These same components of the portable oil monitor 10 are illustrated infront view in FIG. 3 which provides full frontal view of current meter24 and the meter face roll bars 38 mounted to the left and right mostportions of the front panel 22.

FIGS. 4 and 5 provide more detailed views of the electrode assembly 20and the manner in which the electrode assembly is utilized to apply aknown voltage across an electrode gap of predetermined dimensions toinduce a current through the test solution. The magnitude of thatinduced current, when sensed by the measuring circuit to be describedhereinafter in conjunction with FIG. 6, provides a direct indication ofthe relative amount of oil contained in the test sample.

As shown in FIG. 4 electrode assembly 20 includes a pair of electrodeconnector rods 40 and 42. The shorter of the connector rods, 40, iselectrically affixed to the inner-most of two, concentric, circularcylinder electrode rings. The longer electrode connector rod, 42, iselectrically affixed to the outer concentric electrode ring 44 andextends beyond the bottom of the electrode rings to provide a convenientspacer between the electrode rings and the bottom of measuring beaker18. In the preferred embodiment of the invention, the electrode ringsare about 1/2 inch in height, (dimension A in FIG. 4), outer ring 44 hasan outer diameter of 27.587 millimeters (dimension B) and an innerdiameter of 26 millimeters, (dimension C) while the inner ring 46 has aninner diameter of 22.413 millimeters (dimension D) and an outer diameterof 24 millimeters (dimension E). Thus the spacing between rings 44 and46 is about 1 millimeter measured radially from the center of theconcentric rings.

Three permanent magnets 48, 50 and 52 are spaced equidistantly aroundthe outside of beaker 18 to reduce measurement drift problems. As shownin FIG. 4, the north pole of each magnet is oriented at the top of themagnet. A suitable selection for magnets 48, 50 and 52 is ALNICO No. 4.As also previously discussed, the outer ring 44 has four equidistantlyspaced apertures of circular cross section. The combined area of theseapertures is equal to the difference in surface area of the two rings.These four apertures 54, 56, 58 and 60, in addition to providing meansfor equalizing the ring areas, also provide for improved test sampleflow within the gap between the rings.

At the lower most portion of FIG. 4 it may be observed that atemperature sensor diode 62 is located below and in contact with beaker18. This germanium temperature sensor diode is connected to themeasuring circuits, as will hereinafter be described in conjunction withFIGS. 6a and 6b, to provide a means for compensating for temperaturevariations in the test sample so that the current measured between outerring 44 and inner ring 46 through the test sample is relativelyinsensitive to such temperature variations.

Reference will now be had to FIG. 6, which comprises FIGS. 6a and 6b,and which is a detailed schematic diagram of the electronics assembly 30and interface components of the present invention. The purpose of theelectronics portion of the invention is that of providing a means forreading the current induced in the gap between electrode rings 44 and 46through the test solution, in terms of parts per million or parts perbillion oil.

Upon analysis of FIG. 6 by those having skill in the electronics art, itwill be clear that the principal purpose of the circuit thereinillustrated is that of applying the current induced across the testsample between electrode rings 44 and 46 to a differential amplifiercircuit 64 and the amplified output thereof to a monitoring device, inthis case both meter 24 and digital display 28. Additional portions ofthe electronics 30 of the present invention include the switches S1, S2and S3 for turning the system on by applying DC power available fromstored power cells to the electronics and for selecting the appropriatemeter range, namely, 0 to 100 parts per million, 0 to 200 parts permillion, 0 to 1000 parts per million and 0 to 100 parts per billion.Switch S1 is accessible at the top of electronics assembly 30 adjacentdigital display 28 and zero adjust 34, (see FIG. 1 and 2). Switch S2 isaccessible at about the same location but on the other side of zeroadjust 34, (see FIG. 2). Switch S3 is accessible adjacent solventcontainer 16, (see FIGS. 1 and 2).

A trimmer resistance circuit 66 includes the appropriate fixed andvariable value resistances to calibrate the readings for these variousranges. Other adjustable potentiometers are included to zero the meterand display readings and to adjust the operating parameters of amplifiercircuit 64 for proper circuit operation. In addition two relays areprovided, namely, relay 1 and relay 2 which are automatically activatedwhen the power cell voltage levels fall below the values needed toprovide accurate measurement readings of the test sample conductivity.In addition four externally available circuit terminals are provided topermit recharging of the rechargeable power cells when their respectivepower levels diminish below acceptable voltage levels and also toprovide a means for applying a test current to the meter throughamplifier circuit 64 for maintenance and calibration purposes.

As shown at the lower portion of FIG. 6a, three different voltagelevels, namely, 5.2 volts DC, 7.8 volts DC and 1.3 volts DC are used topower the electronics. These voltage levels have been selected so thatone may readily use commercially available 11/2 volt and 9 voltrechargeable power cells, which as commonly known, actually providereliable voltage levels of 1.3 volts and 7.8 volts, respectively. The5.2 volts DC power source, which may be provided by combining four 11/2volt rechargeable batteries in series, is used to provide the powernecessary to drive digital display 28. On the other hand, the 7.8 voltsDC which may be provided by utilizing a 9 volt rechargeable cell, or ifdesired, a plurality of such cells in parallel to extend the operatingtime of the instrument between recharging cycles, and the 1.3 volt DCpower source which may be provided by a 11/2 volt rechargeable powercell or a plurality thereof in parallel for the same reason, areutilized in the apparatus to provide a known voltage level of 9.1 voltsDC and to also provide the voltage levels to power differentialamplifier circuit 64.

Meter 24, shown in the upper right hand corner of FIG. 6a, may beprotected from high voltage transients and the like by means of athyristor TH and is connected to the remaining portion of electronicsassembly 30 by means of a four-pole, double-throw switch S3. Onesuitable meter for use in the present invention is an 18 micro ampd'arsonval, two jewel, four inch needle movement meter. Switch S3, whenin its on configuration, applies the power cell voltages to the circuitto permit use of the electronics for test purposes, and when in an offcondition, removes the power and shorts the meter for protectionthereof. In the off condition of switch S3, the power cells, if they areof the rechargeable type previously discussed, may be recharged byapplying suitable voltages from external sources to the aforementionedterminals shown in the left portion of FIG. 6a.

FIG. 6a also shows the manner in which the electrode assembly 20 isconnected into the electronic assembly 30 of FIGS. 6a and 6b. Thecircuit elements shown in FIG. 6a including meter 24, switch S3, theelectrode assembly and power cell lines, are all appropriately connectedto a 10 pin plug P1 and a two terminal plug P2, both of which havecorresponding mating jacks J1 and J2, respectively, shown in thelower-most portion of FIG. 6b. A 0.25 amp quick-blow fuse is alsoincluded in the circuit of FIG. 6a to provide circuit protection. Aspreviously indicated, this fuse is accessible at the front panel bymeans of fuse holder 26 as discussed previously in conjunction withFIGS. 1 and 3.

Reference will now be made to FIG. 6b for a more detailed indication ofthe manner in which the current through the electrode gap provides ameasurement readout. The objective of the circuit of FIG. 6b is toprovide a measurement of the current induced across the electrode gap inresponse to the application of a known fixed voltage to the circuit inwhich the gap forms a part thereof. As previously indicated, thiscurrent has been made relatively insensitive to temperature by means ofa germanium diode 62 sealed in a TO3 can and located at the bottom ofbeaker 18. It has been found that the temperature can vary from at leastas low as minus 40 degrees Fahrenheit (-40° F.) to as high as plus 176degrees Fahrenheit (+176° F.) without substantially affecting theaccuracy of the measurement, because of the voltage drop compensationversus temperature characteristics of the germanium diode.

As shown at the left-most portion of FIG. 6b, the electrode rods areconnected to terminals A and B of the circuit. Terminal A is connectedthrough junction plug J1 to ground and the voltage at terminal B variesin accordance with the current level through the electrode gap. Thus,the voltage variations at B reflect the variation in conductance of thetest sample in accordance with the oil content thereof. The voltagelevel at terminal B is applied to the gate electrode of FET F2 of thedual FET device within differential amplifier circuit 64. Furthermore,when switch S2 is in the parts per million position, which is theposition illustrated in FIG. 6b, the gate terminal of FET transistor F1is tied to a voltage level of 6.2 volts by means of 6.2 volt zener diodeZ1 which is in series with a 5 Kohm load resistor in the gate circuit ofFET F1.

It is the difference in the voltage levels applied to the respectivegates of FET transistors F1 and F2 that is determinative of the voltageultimately applied, after suitable attenuation for zero adjustment inpotentiometer 34, to the meter and to the digital display 28 for areading that is directly indicative of the oil content of the testsample. The difference voltage applied to the respective gates isamplified by the FET circuit and the amplified signal is applied to therespective source terminals of the FET transistors F1 and F2 which arein turn applied between a fixed terminal and the variable positionterminal of 50 Kohm potentiometer 34, the position of which determinesthe total voltage drop across the two fixed terminals of potentiometer34.

The +M terminal of potentiometer 34 is connected through a voltagedivider network to the positive terminal of meter 24 through jack J2,while the -M terminal of potentiometer 34 is connected through switch S1to the appropriate trim resistor value in trim resistor network 66 tothe negative side of the meter by means of jack J2. There are three suchtrim resistor values corresponding to the three switch values for theranges 0 to 100, 0 to 200 and 0 to 1000 parts per million oil,respectively.

When switch S2 is thrown to the position indicated by dotted lines inFIG. 6b, the bias voltage at the gate terminal FET F1 is reducedconsiderably by removing the 7.8 volts DC from the series load resistorconnected to zener diode Z1 thereby substantially increasing the voltagedifference applied to the meter 24, and making the meter more sensitiveto the subtle changes corresponding to conductivity variations for oillevels in parts per billion. In the parts per billion mode, in theembodiment of the invention illustrated in FIG. 6b, switch S1 ispositioned to be in the zero to 100 range.

The 1.3 volt power cell output is applied to one side of the coil ofrelay 1, the other side of the coil being connected to ground potentialthrough a variable resistor. Similar connections made to the 7.8 voltpower cell output at relay 2. The two variable resistors associated withthe relays are adjusted so that when one or both of the power celllevels drops below a predetermined voltage, the relays are deactivatedand digital display 28 reflects the low voltage situation.

The remaining elements in FIG. 6b are primarily for biasing thedifferential amplifier circuits at the appropriate levels to provideaccurate readings corresponding to the oil content measured in the testsample and to connect display 28 to the appropriate terminals to readand display digital representations of the oil content and also of thepower cell voltage levels during maintenance and calibration of theinstrument.

Now that the chemical and electrical aspects of the process andapparatus of the present invention have been described in detail,typical operation of the invention will be disclosed.

It will be recalled that the apparatus of the present invention has beendeveloped for field use such as maintenance or daily inspection. Forexample, it would be readily useable by petroleum production fieldservice personnel wherein one individual employee is responsible for ablock of, for example, 100 oil wells, pumps, piping, tanks, oil andwater drains and reports to a supervisor when his shift ends. It iscontemplated that under certain circumstances there will be a definiteprogram of periodic testing requested by such supervisor to ascertain ifthe tank or any portion of the well block is losing petroleum oil insignificant quantities to be of economic value if recovered and/or in anamount that exceeds environmental regulations.

When the employee reaches the test site, the test unit is placed onreasonably level ground and the 16 gauge steel cover 12 removed from theapparatus. The 250 milliliter pyrex glass separating funnel 14 is thenremoved from the clamps holding it inside the cover 12. At this pointthe first test sample is taken by holding the separating funnel underthe appropriate discharging pipe or by dipping it into a drainage trenchas required to recover the sample. This is preferable to obtaining thesample with one container and pouring it into a separate sample bottle,since a large error in oil content may occur with use of two vessels inwhich some oil will adhere to the sides of the first container when thesample is poured into the second.

Sufficient sample fluid is taken into the separating funnel 14 to fillthe funnel to the 200 milliliter mark. The solvent and polarity imparterfrom solvent container 16 are added to the extent of 20 milliliters tothe sample in the separating funnel and the entire contents, withstopper in place, are shaken up and down for about 30 seconds to providemaximum interface between the sample liquid and solvent. Then theseparating funnel contents are swirled to aid in consolidating the oil.At least once during violent agitation, the glass stopper of theseparating funnel is removed to vent any gases. If the water phasefloating on top of the solvent-oil sample shows a faint brown color ofoil, the operation should be repeated.

When the separating funnel shows 20 milliliters or more of oil andsolvent at the bottom thereof, the funnel valve is opened and beaker 18is filled to the 15 milliliter line. This leaves 5 milliliters ofsolvent in the narrow taper end of the separater funnel 14 that can beseen clearly. By leaving this additional 5 milliliters of solvent in thefunnel, the operator does not have to use extraordinary skill to stopthe valve at the exact liquid-liquid zone. The sample is now ready totest.

The portable oil monitoring apparatus is turned on by setting switch S3(See FIG. 1) to the ON position. Then range selector switch S1 (SeeFIG. 1) is switched to the appropriate range of oil parts per millionand potentiometer 34 is set to zero the meter at this range. The meterwill quickly reach its reading, allowing the operator to note the oilcontent and record the results. If both the meter and display read zerowith electrode assembly 20 immersed in the test solution in beaker 18,an attempt should be made to read oil content in parts per billion byselecting that mode by means of switch S2 as discussed above inconjunction with FIG. 2.

Examples of actual tests conducted with the inventive apparatus and inaccordance with the steps of the novel process, will now be described.

EXAMPLE I

A 200-milliliter sample of water, suspended solids, and 90 parts permillion (ppm) oil was placed in a mixing container. 20 milliliters oftetrachloromethane solvent already mixed with the polarity imparter wasadded to the sample and manually, violently agitated up and down in themixing container for a period of 30 seconds. After 15 seconds ofagitation, the stopper in the mixing container was removedinstantaneously to vent gas pressure within the mixing container.Following the 30 seconds of agitation, the mixing container was moved ina circular motion to swirl the mixture for another 30 seconds. At theend of the second 30-second period, the mixture in the mixing containerwas separated into a brownish lower phase and a clear upper phase.Suspended solids were visible to the naked eve at the interface of thetwo phases. 15 milliliters of the lower phase was drained out through adrain valve at the bottom of the mixing container leaving the upperphase and the suspended solids in the mixing container.

EXAMPLES II and III

The procedure described in Example I above was repeated first withtetrachloroethylene used in lieu of tetrachloromethane and secondly withtetrachloroethane used in lieu of tetrachloromethane. The resultsobtained were the same as described above in Example I.

EXAMPLE IV

To determine the amount of oil in a 200-milliliter sample of oil,suspended solids and water, chromium dicarbide particles of 0.2 micronssize were provided by mechanically reducing the material to 0.2 micronsor less. The colloidal particles were then mixed with tetrachloromethaneto provide a colloidal gel. Three parts by volume of the colloidal gelwas then mixed with 97 parts by volume of tetrachloromethane. 5.1milliliters of this mixture were then mixed with 24.9 milliliters of thesolvent to provide a solvent conductivity additive mixture.

The procedure described in Example I above was then repeated using thesolvent conductivity additive mixture in lieu of the solvent of ExampleI, and 15 milliliters of the brownish lower phase was drained throughthe drain valve at the bottom of the mixing container back into thebeaker used for introducing the solvent-conductive additive mixture tothe mixing container. This left the suspended solids within the mixingcontainer. An electric current was then passed through the 15milliliters of brownish lower phase material using the apparatusdescribed above in conjunction with FIGS. 1 through 6, readout on thedial of the apparatus showed 90 ppm of oil.

It will now be apparent that what has been described herein are a novelmethod and apparatus that permit measurement of the relative amount ofsaturated hydrocarbon oil and all unsaturated hydrocarbon oils that willnot support a reaction in the presence of water or liquid immisciblewith the oil. Numerous novel features of the inventive process andapparatus have been disclosed that are believed, for the first time, toenable accurate field-site measurement of small quantities of such oilsin water and other liquids immiscible with oil. A preferred embodimentof the novel apparatus of the present invention has been disclosed as ameans for carrying out the inventive process. Such apparatus provides adirect readout of relative oil content and permits such measurements tobe made quickly and conveniently in the field by personnel having nospecial skill.

It will now be apparent to those familiar with the art to which thepresent invention pertains that in addition to the novel process andapparatus disclosed herein, certain novel features thereof have alsobeen disclosed which although designed specifically for operation in thepresent invention, are readily adaptable to a variety of other uses notnecessarily associated with the process of measuring oil content. By wayof example, a novel electrode assembly has been disclosed and a novelmagnetic stirring mechanism has been disclosed for use therewith. Bothsuch features may be applied advantageously in other fields notnecessarily related to the present invention. However, it will beunderstood that all such novel advantageous features, whether or notused in the process and apparatus of the present invention, arecontemplated to be within the scope of the inventive contributionsdisclosed herein.

Having thus described a preferred embodiment of the invention what isclaimed is:
 1. A method of measuring relatively small amounts ofhydrocarbon oil comprising:providing a sample which includes saturatedhydrocarbon oil and a first liquid which is immiscible with the oil;providing an essentially nonconductive solvent which is essentially notsoluble in the first liquid and which extracts the oil from the firstliquid; providing a conductivity additive which renders hydrocarbon oilelectrically conductive but does not render the solvent electricallyconductive; mixing the sample, the solvent and the conductivity additivein a container to cause the solvent to extract oil from the first liquidto form a mixture including the oil, the solvent, and the conductivityadditive with the conductivity additive rendering the oil of the mixtureelectrically conductive, said first liquid and said mixture havingdifferent specific gravities whereby said mixture and said first liquidare in essentially distinct layers in said container; passing saidmixture between electrodes having a known voltage differencetherebetween, after the oil is rendered conductive; and measuring thecurrent induced between said electrodes to obtain an indication of theamount of oil in said mixture.
 2. A method as defined in claim 1,wherein said conductivity additive includes colloidal metal-containingparticles having a particle size of about 0.2 microns dispersed in thesolvent.
 3. An apparatus for measuring relatively small amounts ofhydrocarbon oil contained in a liquid which is immiscible with the oil,the apparatus comprising:a mixing container for containing said oil andliquid, solvent means for separating said oil from said liquid to form asolvent-oil mixture in said container; means for adsorbing colloidalmetal-containing particles on said hydrocarbon oil of said mixture insaid container to render said hydrocarbon oil conductive withoutrendering said solvent conductive; and means for measuring theconductivity of said mixture including said metal-contaning particles toprovide an indication of the relative amount of said hydrocarbon oil insaid liquid.
 4. The apparatus as defined in claim 3, wherein saidconductivity measuring means comprises:a pair of electrodes having a gaptherebetween in which said mixture, including said metal-containingparticles may be caused to flow; means for applying a voltage differencebetween said electrodes across said gap; and means for providing ameasurement indication dependent upon the current induced between saidelectrodes across said gap.
 5. An apparatus for measuring relativelysmall amounts of hydrocarbon oil contained in a liquid which isimmiscible with oil, the apparatus comprising:a mixing container forcontaining said oil and liquid, solvent means for separating said oilfrom said liquid to form a solvent-oil mixture in said container; meansfor adsorbing colloidal metal-containing particles on said hydrocarbonoil of said mixture in said container to render said hydrocarbon oilconductive without rendering said solvent conductive; electrode meansfor immersion in said mixture including said metal-containing particles;said electrode means comprising a pair of concentric cylinders radiallyspaced from one another to form a circumferential gap therebetween, anda pair of electrically isolated connecting rods for connecting saidcylinders, respectively, to separate terminals of an electrical circuit;and an electrical circuit for connection to said rods and having meansfor applying a known voltage across said circumferential gap throughsaid mixture including said metal-containing particles, and having meansfor amplifying the current induced in said gap and measuring saidamplified current to provide an indication of the relative amount ofsaid hydrocarbon oil in said liquid.